1. Field of the Invention
The present invention relates to coatings and binders for pharmaceutical forms which contain a copolymerizate of ethylenic, unsaturated, radical and polymerizable monomers with a carboxyl group and alkyl esters of such monomers which are present, preferably as latex dispersed in an aqueous phase, as well as to the use of the coatings and binders and the pharmaceutical forms produced with them.
2. Description of the Background
From DE-C 2,135,073, coatings for pharmaceutical forms are known in the form of an aqueous dispersion. These coatings contain emulsion polymerizates which, in general, are made up of 50 wt % methyacrylic acid and 50 wt % methyl or ethyl acrylate. A binder of this type is known in commerce under the trade name, EUDGRAGIT L30D (trademark of Rohm GmbH, Darmstadt).
Drug coatings produced from this binder are insoluble in the acid milieu of the gastric juice, and dissolve in gastric juice only at a pH value of 5.5 and more, and then release the core containing the active ingredient for dissolution. For different active ingredients, different release characteristics are desirable. Some pharmaceutical forms are intended to release the active ingredient immediately after entry of the pharmaceutical form into the duodenum or the upper intestinal section at pH values of approximately 5 to 6, while others do not do so until entering the lower intestinal areas, as far as the colon, at pH values of approximately 6 to 7.5. For this reason, a sufficiently broad palette of coating agents is desired for different release pH values in order to control the release of the active ingredient in these sections of the intestine.
The release characteristics of drug coatings in vitro are tested according to USP, normally with artificial gastric juice (0.1N HCl) and artificial intestinal juice (pH 6.8). In order to determine the gradual dissolution in the intestinal region, it has proven expedient to determine the release rate of a water-soluble substance from the pharmaceutical form first within 2 h in artificial gastric juice, and then in buffer solutions, and, beginning at pH 5.0, to change the buffer solution every 60 min, whereby the pH value is gradually increased by 0.5 in each case.
From EP-B 152,038, aqueous coating agents are also known which also allow the production of pharmaceutical forms with a release pH of value of 7 to 7.5. However, this requires the mixing of at least two coating dispersions, of which one is responsible for pH control and the other for the adjustment of elasticity. This neutral polymerizate component is, however, insoluble in the gastric juice and frequently causes an undesirable delay of dissolution even after the desired pH value has been reached.
Thus, a need exists for a coating agent which can be used in the form of an aqueous dispersion and which dissolves in the deeper areas of the intestine or colon, and which allows release of the coated active ingredient when an acceptable pH level is reached.